The driving of steel pipes through the ground, for example with the help of a pneumatic rammer which has a part-conical driving nose engaging directly or via a driving cap into the rearward end of the pipe, which is guided on bearing blocks and has a driving shoe fitting over both the inside and the outside of the forward end, has become increasingly common. Since the driven pipe is open at its forward end, that is at the driving shoe, the soil through which the pipe is driven penetrates during driving further and further into the interior of the pipe, while the driving shoe compacts the soil surrounding the pipe. Because the driving shoe has a larger external diameter than that of the pipe, it creates a channel in the soil, through which the driven pipe moves forwards under the impact of the rammer with comparatively low wall friction.
As the interior of the pipe becomes increasingly filled with soil as driving advances, the soil friction against the inner face of the pipe also increases. This occurs particularly when the soil inside the pipe becomes more and more compacted under the influence of the driving impacts and of the soil being forced into the pipe from its forward end. Furthermore, the soil inside the pipe has to be accelerated with the forward movement of the pipe. Because of this an additional consumption of total energy by the rammer results. Moreover, the soil must from time to time be removed from the driven pipe. A number of techniques for removing the soil from the interior of the pipe are known. Thus, for example, the soil can be removed from the pipe interior by means of a screw conveyor within the pipe. This, however, like the flushing out of the soil with high-pressure water, requires the expense of additional equipment and is accompanied by considerable interruptions in driving. In another technique for removing the soil from the pipe interior, after driving has been terminated a thrust disc which bears sealingly against the inner face of the wall of the pipe is fitted into the forward end of the pipe and the interior of the pipe in front of the disc is subjected to compressed air, in order to force the soil counter to the direction of driving out of the pipe by movement of the thrust disc along the pipe under the air pressure. This technique is also complicated and expensive and moreover can only be used for short pipe lengths and with low frictional resistance, on account of the friction of the soil against the inner face of the wall of the pipe.